1. Technical Field
The present disclosure relates to a magnetic sensor integrated in a chip for detecting magnetic fields perpendicular to the chip and to the manufacturing process thereof.
2. Description of the Related Art
Various sensors are known that are able to detect magnetic fields parallel to the surface of a chip integrating the sensor. On the other hand, production of magnetic sensors sensitive to magnetic fields perpendicular to the surface of a chip (for example, for electronic compasses) is problematic. In fact, integrated magnetic sensors currently available on the market are substantially sensitive to fields directed parallel to the plane of the sensor (plane XY), and a sensor that is sensitive along the axis Z is obtained by arranging the chip of the corresponding sensor in a direction perpendicular to the chips of the X and Y sensors. However, in this case, the assembly and calibration operations are complex, and the finished device is costly. In addition, the packaged device has a large volume (in particular, in height), which does not enable use thereof in small apparatuses.
In order to solve this problem, it has already been proposed to use a Hall-effect sensor overlaid by a magnetic structure that collects and concentrates vertical magnetic fields perpendicular to the chip (see, for example, patent abstracts JP2000340856 and U.S. Pat. No. 6,396,114). These solutions are, however, sensitive to the magnetic fields directed in a transverse direction (parallel to the chip), which are not separated from perpendicular magnetic fields. In fact, the presence of horizontal portions (parallel to the chip surface) or portions having a horizontal component causes a deformation of the magnetic field directed parallel to this portion, and thus reading errors.
US2011/0193556 describes embodiments of an integrated magnetic sensor wherein a concentrator of ferromagnetic material extends as far as near a Hall sensor. Here, the absence of magnetic or ferromagnetic layers parallel to the chip reduces the effects of parallel magnetic fields. Moreover, the distance between the concentrator and the Hall sensor determines in any case a loss of field lines of the concentrated field in the area between the concentrator and the Hall sensor, loss that cannot be eliminated since the ferromagnetic material may be a source of silicon contamination and may alter operation of the Hall-effect cell.